feat: review open answers in the admin and pick a grader per quiz

- Do oceny admin screen (golem15.quizzes.reviews) over the open answers,
  with a read-only context partial, score and comment virtual fields saved
  through SetScore, confirm and regrade record actions, bulk confirm
- open question type, rubric and max_length in the question form; grader
  dropdown on the quiz form from the grader registry
- Review model with quiz, status and student filters

plugin_test.go

@@ -36,8 +36,8 @@ func TestPluginActivates(t *testing.T) {
 	if got := p.Requires(); !slices.Equal(got, []string{"golem15.user"}) {
 		t.Errorf("Requires = %v, want golem15.user", got)
 	}
-	if got := len(p.(pact.HasModels).Models()); got != 5 {
-		t.Errorf("Models = %d, want 5", got)
+	if got := len(p.(pact.HasModels).Models()); got != 6 {
+		t.Errorf("Models = %d, want 6", got)
 	}
 	migrations := p.(pact.HasMigrations).Migrations()
 	if len(migrations) == 0 {